fix: Ignore existing Robotoff questions when reloading

[g123k]

Hi everyone!

My previous PR (#6078) was not strict enough to remove the Robotoff banner.
Basically, if the API still returns the same questions, the banner will reappear.

We now ensure that after answering questions AND if questions are the same, the banner won't be displayed.

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 0% with 22 lines in your changes missing coverage. Please review.

Project coverage is 6.38%. Comparing base (4d9c7fc) to head (8615991).
Report is 612 commits behind head on develop.

Files with missing lines	Patch %	Lines
...ooth_app/lib/helpers/robotoff_question_helper.dart	0.00%	9 Missing ⚠️
...b/pages/product/product_page/new_product_page.dart	0.00%	7 Missing ⚠️
...pp/lib/pages/product/product_questions_widget.dart	0.00%	6 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           develop   #6130      +/-   ##
==========================================
- Coverage     9.54%   6.38%   -3.17%     
==========================================
  Files          325     449     +124     
  Lines        16411   25515    +9104     
==========================================
+ Hits          1567    1628      +61     
- Misses       14844   23887    +9043     

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[teolemon]

thanks Edouard 👍